Bacterial, Archaeal and Fungal Succession in the Forefield of a Receding Glacier

Glacier forefield chronosequences, initially composed of barren substrate after glacier retreat, are ideal locations to study primary microbial colonization and succession in a natural environment. We characterized the structure and composition of bacterial, archaeal and fungal communities in exposed rock substrates along the Damma glacier forefield in central Switzerland. Soil samples were taken along the forefield from sites ranging from fine granite sand devoid of vegetation near the glacier terminus to well-developed soils covered with vegetation. The microbial communities were studied with genetic profiling (T-RFLP) and sequencing of clone libraries. According to the T-RFLP profiles, bacteria showed a high Shannon diversity index (H) (ranging from 2.3 to 3.4) with no trend along the forefield. The major bacterial lineages were Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Cyanobacteria. An interesting finding was that Euryarchaeota were predominantly colonizing young soils and Crenarchaeota mainly mature soils. Fungi shifted from an Ascomycota-dominated community in young soils to a more Basidiomycota-dominated community in old soils. Redundancy analysis indicated that base saturation, pH, soil C and N contents and plant coverage, all related to soil age, correlated with the microbial succession along the forefiel

Bacterial and fungal community responses to reciprocal soil transfer along a temperature and soil moisture gradient in a glacier forefield

The influence of soil physicochemical properties on microbial communities can be large, especially in developing soils of glacier forefield chronosequences. However, small-scale expositional differences in bare soils and their impacts on soil microbial communities have so far been largely neglected. Here we studied the changes of microbial communities in three deglaciated unvegetated sites along a soil moisture and temperature gradient near a glacier terminus. In order to elucidate the driving forces for these changes, fine granite sediment was reciprocally transferred and regularly sampled during 16 months to determine microbial activities and the bacterial and fungal community structures and compositions using T-RFLP profiling and sequence analysis. Microbial activities only responded to soil transfer from the warmer and drier site to the colder and moister site, whereas the bacterial and fungal community structures responded to transfer in both directions. Bacterial phylotypes found to react to soil transfer were mainly the Acidobacteria, Actinobacteria, alpha- and beta-Proteobacteria. The common fungal phylogenetic groups Pezizomycetes and mitosporic Ascomycetes also reacted to soil transfer. It seemed that the soil moisture was the limiting factor for the microbial activities. We concluded that for the microbial community structures transferring soil from a colder to a warmer site induced a higher rate of change due to a higher microbial activity and faster species turnover than the reverse transfer. (C) 2013 Elsevier Ltd. All rights reserved

Molecular characterization of phototrophic microorganisms in the forefield of a receding glacier in the Swiss Alps

Recently deglaciated areas are ideal environments to study soil formation and primary microbial succession where phototrophic microorganisms may play a role as primary producers. The aim of our study was to investigate the cyanobacterial and green algal community composition in three different successional stages of the Damma glacier forefield in the Swiss Alps using 16S rDNA and ITS rDNA clone libraries. Cyanobacterial target sequences varied along the glacier forefield, with the highest cyanobacterial 16S rRNA gene copies found in sparsely vegetated soils. Sequence analysis revealed that the phototrophic communities were distinct in each of the three soil environments. The majority of the cyanobacterial sequences retrieved from barren soils were related to the Oscillatoriales. The diversity in sparsely vegetated soils was low, and sequences closely related to Nostoc sp. dominated. The majority of the algal phylotypes are related to members of the Trebouxiophyceae known to live as symbiotic partners in lichens. We conclude that the community composition appears to shift markedly along the chronosequence, indicating that each soil environment selects for its phototrophic community. When cyanobacteria occur together with eukaryotic microalgae, they form a rich source of organic matter and may be important contributors of carbon in nutrient-deficient deglaciated soils.ISSN:1748-9326ISSN:1748-931

Methane and Carbon Dioxide Fluxes from a European Alpine Fen Over the Snow-Free Period

Wetlands play an important role in the global carbon cycle and are sources and sinks for the greenhouse gases methane (CH4) and carbon dioxide (CO2). We provide an in situ study on variability of daytime CH4 emissions and net ecosystem CO2 exchange (NEE) from a permanently submerged, Carex rostrata dominated Swiss alpine fen over the snow-free period (June-October). Flux chamber measurements were combined with analyses of above-ground biomass and physico-chemical pore water properties. The fen was a net daytime CH4 source throughout the snow-free period, and emissions varied significantly between the sampling dates, ranging from 3.1 ± 0.9mg CH4 m−2 h−1 in October to 8.0 ± 2.9mg CH4 m−2 h−1 in August. The fen was generally a daytime sink for CO2, and net CO2 emission was only observed in late October. Variations in NEE were more pronounced than variations in CH4 emissions, but both fluxes correlated with changes in green C. rostrata biomass and subsurface temperatures. Methane and CO2 pore water concentrations also varied significantly over the snow-free period, decreasing and increasing, respectively. These variations were linked to the development of biomass, but CH4 emissions and NEE were not correlated with the respective pore water concentrations

Methane and Carbon Dioxide Fluxes from a European Alpine Fen Over the Snow-Free Period

Wetlands play an important role in the global carbon cycle and are sources and sinks for the greenhouse gases methane (CH4) and carbon dioxide (CO2). We provide an in situ study on variability of daytime CH4 emissions and net ecosystem CO2 exchange (NEE) from a permanently submerged, Carex rostrata dominated Swiss alpine fen over the snow-free period (June–October). Flux chamber measurements were combined with analyses of above-ground biomass and physico-chemical pore water properties. The fen was a net daytime CH4 source throughout the snow-free period, and emissions varied significantly between the sampling dates, ranging from 3.1 ± 0.9 mg CH4 m−2 h−1 in October to 8.0 ± 2.9 mg CH4 m−2 h−1 in August. The fen was generally a daytime sink for CO2, and net CO2 emission was only observed in late October. Variations in NEE were more pronounced than variations in CH4 emissions, but both fluxes correlated with changes in green C. rostrata biomass and subsurface temperatures. Methane and CO2 pore water concentrations also varied significantly over the snow-free period, decreasing and increasing, respectively. These variations were linked to the development of biomass, but CH4 emissions and NEE were not correlated with the respective pore water concentrations.ISSN:0277-5212ISSN:1943-624

Bovine herpesvirus 5 BICP0 complements the bovine herpesvirus 1 homolog

Bovine herpesvirus 1 (BoHV-1) and BoHV-5 are closely related (82% amino acid identity) but differ strongly in neuropathogenesis. The immediate-early gene for BICP0 is less conserved (70% amino acid identity) and may contribute to a dissimilar phenotype. A peculiar difference is a guanosine hexamer in the BICP0-1 gene which aligns with only five guanosines in the BICP0-5 gene and therefore results in a frameshift in the latter open reading frame. Thus, the C-terminal amino acid sequence (residues 643–676 of BICP0-1 vs. 655–720 of BICP0-5) is completely different. We introduced the BICP0-5 frameshift into the BoHV-1 genome cloned as a bacterial artificial chromosome (BoHV-1 BAC) using the Red recombination system with galK selection and counterselection. Transfection of MDBK cells with the resulting BAC produced recombinant virus that replicated like wild type BoHV-1 in vitro. Attempts to exchange the entire BICP0-1 gene by the BoHV-5 homolog using the same approach failed repeatedly. Therefore, we cotransfected purified BICP0/galK+-BoHV-1 BAC DNA with a recombination plasmid coding for BICP0-5 with or without a HA tag into MDBK cells. BoHV-1 recombinants expressing the respective proteins were characterized. In vitro, all recombinants grew to similar titers as the parental viruses, which demonstrates that BICP0-5 compensates for the growth defect of BICP0/galK+-BoHV-1 and functionally complements BICP0-1 of BoHV-1. We conclude that BICP0 may be suitable to positively select BoHV-1 recombinants with deletions or insertions of additional genes of interest

Bacterial, Archaeal and Fungal Succession in the Forefield of a Receding Glacier

ISSN:1432-184XISSN:0095-362